Description:
------------
Session.compat_42 warning message is reported without using global variables as a source of data.  Register globals are off.  

This warning message occurs when a local variable and a session variable have the same name, and the session variable ends up being assigned a NULL value - see code below.  (Note: I'm not trying to unset the session variable. In my real code, the NULL result came from several levels of nested function calls).

This warning message states "...the session extension does not consider global variables as a source of data, unless register_globals is enabled".  This does not describe this siutation.

The documentation doesn't state that local variables and session variables must not have the same name; and the comp_42 warning message does not cover this case either.  So this must be a bug.







Reproduce code:
---------------
    session_start();

    // WORKS:
    //   $x = 1; 
    //   $_SESSION["x"] = "";   
    // or
    //   $_SESSION["x"] = NULL;   

    // FAILS with session.bug_compat_42 warning: 
       $x = 1; 
       $_SESSION["x"] = NULL; 


Expected result:
----------------
No warning messages and not having to disable warning messages that do not describe this situation.  (Or changes to the documentation stating "local variables and session variables can not have the same names").

Actual result:
--------------
Warning: Unknown(): Your script possibly relies on a session side-effect which existed until PHP 4.2.3. Please be advised that the session extension does not consider global variables as a source of data, unless register_globals is enabled. You can disable this functionality and this warning by setting session.bug_compat_42 or session.bug_compat_warn to off, respectively. in Unknown on line 0